Comparison of in vitro effects of cadmium and nickel on the components of the liver microsomal drug metabolizing enzyme system of the guinea-pig.

In vitro addition of cadmium chloride (CdCl2) to a reaction mixture decreased the liver microsomal cytochrome P-450 level of the male guinea-pig. In contrast nickel chloride (NiCl2) did not cause any alteration in the cytochrome P-450 level. Neither CdCl2 nor NiCl2 produced any activity changes in the liver microsomal NADPH-cytochrome c reductase. When the liver microsomes were preincubated in the presence of CdCl2, metal-induced reduction increased as the time of preincubation progressed and attained its maximum reduction level at about 15 min. In the case of NiCl2, the maximal reduction level was attained at about 5 min. However, no changes were observed by metals in liver microsomal NADPH-cytochrome c reductase activity as the time of preincubation progressed. After preincubation, the reduction of cytochrome P-450 achieved by CdCl2 was stronger than that obtained by NiCl2 as well as than that obtained by CdCl2 without preincubation.